1. Field of the Invention
The present invention relates to a motor and more specifically to a motor for use in an electric centrifugal fan that blows air.
2. Description of the Related Art
There are two types of blower fans: axial fans and centrifugal fans. In general, the axial fans have excellent air volume characteristics, while the centrifugal fans have excellent static pressure characteristics.
Excellent static pressure characteristics, rather than excellent air volume characteristics, are generally required for the purposes of cooling electronic devices, such as notebook computers, inside of which electronic components are densely packed. In particular, the centrifugal fans are generally chosen as small-sized blower fans which are used to cool the notebook computers.
Inside a housing of the centrifugal fan, an impeller portion including a plurality of blades is typically arranged on an outside surface of a hub which is in the shape of a covered cylinder and which defines a portion of a motor. The centrifugal fan is arranged to suction air in an axial direction, and discharge the air in a radial direction. The housing of the centrifugal fan typically includes a base to which the motor is fixed, a side wall which defines a channel for air, and a cover which is arranged to cover an upper end of the side wall.
In recent years, electronic devices, such as personal computers, have been becoming smaller and smaller. There is accordingly a demand for a reduction in size and thickness of the centrifugal fans.
In a related-art technique, locking claws are provided in a metallic frame, and a housing arranged to hold a bearing is engaged with the frame through the locking claws, for example.
In this technique of engaging the housing with the frame through the locking claws provided in the frame, however, the locking claws have to be arranged at regular intervals in a circumferential direction while having a wide radial spread on the frame. Because the wide radial spread of the locking claws on the frame is indispensable, a reduction in a radial dimension of the fan is limited.
Moreover, when a reduction in an axial dimension of the fan is aimed at by placing a circuit board as close to the frame as possible, the locking claws provided in the frame may come into contact with the circuit board, which then renders the circuit board unstable. In order to achieve a reduction in the axial dimension of the fan in conjunction with this related-art technique, ingenuity would be therefore required with respect to the shape and arrangement of the circuit board so as to prevent the circuit board from coming into contact with any locking claw provided in the frame.